可变数据类型及其更改

Question

I am trying to find out a data type of a certain variable (it is a column in a db in RoR application). I would like to format it as a number with 2 decimals, but I want to first find out if it is a string or an integer.

• How can I find out?
• How can I change it? (And do I need to)
• How do I format it to two decimals, whatever the original is?
• What is the best way to go about this - change it in css? in js? in the variable type?

Answer 1

For the format of your 2-decimals number, see this post What is the best method of handling currency/money?

The best way to do is to not change it, and register it directly with rails.

If you have to change a string to a 2-decimal number, create a migration with

• add_column my_decimal_number
• execute an DB query to update your table from my_string_number to my_decimal_number
• deletes my_string_number

Answer 2

• The data type is specified in the database schema (schema.rb)
• If you want to change it from string -> integer, you have to write a database migration.
• The best way to implement it would probably be in a view helper. (see http://guides.rubyonrails.org/getting_started.html#view-helpers )